KR20060043802A - Magnetron for microwave oven - Google Patents

Abstract

An object of the present invention is to provide a magnetron for a microwave oven capable of suppressing unnecessary noise, in particular, the sixth harmonic and the seventh harmonic.

A cathode 12 positioned inside the anode cylinder 11, a plurality of vanes 13 disposed radially from the inner wall of the anode cylinder 11 toward the cathode 12, and a plurality of vanes 13. 1st strap ring 14a which connects every other one, and the 2nd strap ring 14b which is located inside this 1st strap ring 14a, and connects several vanes every other, and oscillation frequency In a microwave oven magnet having a band of 2450 MHz, the inner diameter of the second strap ring 14b is 1.45 to 1.53 times the distance between the inner ends of the two vanes 13 positioned on the diameter of the anode cylinder 11. to be.

Microwave oven magnet, cylinder, vane, strap ring

Description

Magnetron for microwave oven {MAGNETRON FOR MICROWAVE OVEN}

1 is a schematic cross-sectional view illustrating an embodiment of the present invention.

Fig. 2 is a view for explaining an embodiment of the present invention, and a top view schematically showing the main part of the anode.

Fig. 3 is a schematic cross-sectional view illustrating an oscillation unit including an anode, illustrating an embodiment of the present invention.

4 is a cross-sectional schematic diagram mainly illustrating an output unit for explaining an embodiment of the present invention.

5 is a characteristic diagram illustrating an embodiment of the present invention.

6 is a characteristic diagram illustrating an embodiment of the present invention.

<Explanation of symbols for the main parts of the drawings>

11: anode cylinder

12: cathode

13: vane

15: first pole piece

16: second pole piece

17: cooling fin

19: first metal ring

20: second metal ring

22: sealing ring

23: exhaust pipe

25: antenna

30: conductive gasket

The present invention relates to a microwave oven magnetron for use in a high frequency heating source of a microwave oven.

The microwave magnetron is an electromagnetic tube generating high frequency, and the oscillating main body part is composed of a cathode cylinder and a cathode located in the inner space of the anode cylinder, and a plurality of vanes disposed radially from the inner wall of the anode cylinder toward the cathode. have.

In the above-described configuration, the high frequency power generated from the input portion to the cathode and generated in the oscillation main body portion is taken out from an output portion such as an antenna to the outside.

In operation, the magnetron for microwave ovens generates a noise ranging from several hundreds of frequencies to several tens of frequencies in addition to a fundamental wave of 2450 MHz. The noise leaks to the outside through an antenna constituting the output unit or an input terminal for supplying power to the cathode, thereby preventing various communications.

Therefore, various methods for suppressing noise have been proposed in the conventional magnetron for microwave ovens. For example, a choke structure for preventing high frequency is provided at the output part, and a filter circuit composed of a through condenser and a choke coil is provided at the input part.

The conventional magnetron for microwave ovens suppresses unwanted noise such as harmonics by a choke structure having a length of 1/4 of the wavelength? For the purpose of suppressing harmonics provided in the output section, and a filter circuit provided in the input section.

By the way, in the case of the microwave oven in which the magnetron for microwave oven is assembled, the frequency range applied by the Comite International Special des Perturbations Radioelectriques / International Special Committee on Radio Interference (C.I.S.P.R) is up to the fifth harmonic until now. Therefore, the conventional magnetron for a microwave oven has a structure which can fully respond to the high frequency interference to 5th harmonic. In order to suppress the fifth harmonic, a technique of setting a predetermined position of the strap ring on the anode vane instead of the choke is disclosed in Japanese Patent Laid-Open No. Hei 1-45936. However, this technique has some effect on the suppression of the fifth harmonic, but it is not enough. For this reason, even when such strap ring position adjustment is used, the fifth harmonic choke is provided on the output upper side and used in combination. Usually, the inner diameter of the inner ring of the strap ring is set to 1.6 times or more of the distance between the inner ends of two vanes positioned on the diameter of the anode cylinder in consideration of the oscillation efficiency. In this structure, however, higher harmonics may not be sufficiently suppressed.

An object of the present invention is to provide a microwave oven magnetron capable of suppressing unnecessary noise, in particular, the sixth harmonic and the seventh harmonic.

According to the present invention, a pair of anodes alternately connected to each other in the upper and lower portions of a cathode positioned inside the anode cylinder, a plurality of vanes arranged radially from the inner wall of the anode cylinder toward the cathode direction, A magnetron for a microwave oven having a first strap ring and a pair of second strap rings positioned inward from the first strap ring and alternately connected to each other from above and below the plurality of vanes and having an oscillation frequency of 2450 MHz. The inner diameter of the second strap ring is 1.45 to 1.53 times the distance between the inner end portions of the two vanes positioned on the diameter of the anode cylinder.

According to the present invention, the inner diameter of the small second strap ring located inside is set to 1.45 times to 1.53 times the distance between the inner ends of the two vanes located on the diameter of the anode cylinder, and unnecessary harmonics, in particular, the sixth And a magnetron suppressing the seventh harmonic is realized.

An embodiment of the present invention will be described with reference to FIG.

The spiral-wound negative electrode 12 is arrange | positioned inside the positive electrode cylinder 11 which comprises the oscillation main body part of the microwave oven magnetron. The cathode 12 is arrange | positioned along the tube axis m. Further, even vanes 13 are provided from the inner wall of the anode cylinder 11 toward the cathode 12 and at equal intervals in the circumferential direction of the anode cylinder 11. The outer end of the vane 13 is fixed to the inner wall of the anode cylinder 11, and the inner end is a free end. The illustrated upper and lower sides of each vane 13 are located inside the pair of first strap ring 14a and the first strap ring 14a having a larger diameter, respectively, than the first strap ring 14a. The small pair of second strap rings 14b are alternately connected to each other.

For example, the upper edge of the vane 13 is counted from one vane 13, and the odd numbered vanes 13 are connected in the first strap ring 14a, and the even numbered vanes 13 are connected to each other. It is connected by the 2nd strap ring 14b. On the contrary, the lower side of the vane 13 is connected to the odd numbered vanes 13 in the second strap ring 14b, and the even numbered vanes 13 are connected in the first strap ring 14a. have.

The first pole piece 15 and the second pole piece 16 are disposed in the upper and lower opening portions of the anode cylinder 11, and a plurality of cooling pieces for cooling the anode cylinder 11 around the anode cylinder 11. The pin 17 is arranged.

The first metal container 18 is hermetically bonded to the first pole piece 15, and the first metal ring 19 is hermetically bonded to the first metal container 18. The second metal ring 20 is bonded to the first metal ring 19, and the insulating cylinder 21 is hermetically bonded to the second metal ring 20. In addition, the sealing ring 22 is hermetically bonded to the insulating cylinder 21, and the exhaust pipe 23 is sealed to the sealing ring 22. The sealing ring 22 and the exhaust pipe 23 are protected by a cap 24. In addition, one end of the antenna 25 constituting the output unit is connected to the exhaust pipe 23. The other end of the antenna 25 is connected to one vane 13 through an inner space such as an insulating cylinder 21.

In addition, double cylindrical wall structure portions C3 and C5 are formed in portions such as the first metal container 18 and the second metal ring 20, and one-quarter of the so-called wavelength? That suppresses harmonics. A choke structure having a length is provided.

In addition, a second metal container 26 is hermetically bonded to the second pole piece 16, and a cathode system 27 which becomes part of the input unit 60 to the second metal container 26 is connected to the tube axis m. Therefore, it is extended and fixed.

Annular permanent magnets 28a and 28b are disposed above the first pole piece 15 and below the second pole piece 16. Moreover, the magnetic yoke 29 which forms a magnetic path so that the anode cylinder 11, the cooling fin 17, and the permanent magnets 28a and 28b may be arrange | positioned is arrange | positioned. A conductive gasket 30 is provided on an inner portion of the magnetic yoke 29 surrounding the first metal ring 19.

In addition, a center rod 31 and a side rod 32 are disposed in the inner portion of the cathode system 27. The center rod 31 is connected to the end hat 12a of the output side end located above the cathode 12, and the side rod 32 is connected to the input side end located below the cathode 12 shown. Doing. A coil 33 and a condenser 34 constituting a filter circuit are connected to an outer portion of the cathode system 27.

The negative electrode system 27 and the coil 33 are surrounded by the filter case 35, and the capacitor 34 is attached to penetrate the filter case 35.

Next, FIG. 2 shows a partial longitudinal section of the main part of the oscillation part as shown in FIG. 2 from the upper portion of the anode portion constituting the oscillation main body portion, as shown in FIG. It demonstrates with reference to 3. 2 and 3 omit the overlapping description by attaching the same reference numerals to the parts corresponding to FIG. 1.

In the inner space of the anode cylinder 11, a plurality of, for example, ten vanes 13a to 13j are provided at equal intervals in the circumferential direction of the anode cylinder 11 and from the inner wall of the anode cylinder 11 toward the center direction. It is. At this time, two vanes 13 are opposed to each other on the diameter of the anode cylinder 11, for example, 13a and 13f, 13b and 13g,... Are located in pairs.

Here, the inner diameter of the anode cylinder 11 is 2rv, and the distance between two vanes located on the diameter of the anode cylinder 11, for example, the distance between the vane 13a and the inner end of the vane 13f is 2ra, the first strap. The outer diameter of the ring 14a is LS, and the inner diameter of the second strap ring 14b is SS.

In addition, in the present invention, the ratio (2ra / 2rv) between the inner diameter 2rv of the anode cylinder and the distance 2ra between the vane tip portions is in the range of 0.22 to 0.28, and the distance between the outer diameter LS of the first strap ring and the vane tip portion ( The ratio LS2ra with 2ra) is a design condition of the resonator in the range of 2 to 2.3, and the ratio (SS / 2ra) of the inner diameter SS of the second strap ring and the distance 2ra between the vane tip is used as the design condition of the resonator. ) Is set in the range of 1.45 to 1.53.

In the above-described configuration, power is supplied from the input unit 60 to the cathode 12 so that the high frequency generated at the oscillation main body part is taken out through the output unit 50 made of the antenna 25 or the like.

In operation, the magnetron for a microwave oven generates a noise ranging from several hundreds of radio waves to several tens of radio waves in addition to a fundamental wave of 2450 MHz (± 50 MHz). As shown in Fig. 1, these noises are provided on the choke C2 provided on the upper part of the output part 50, the choke C3 provided on the middle of the output part, the choke C5 and the input part 60 side. Leakage to the outside is suppressed by the filter circuit.

Next, the suppression of the sixth and seventh harmonics will be described. In addition, the general dimension of the anode part of a microwave oven magnetron is as follows.

Anode inner cylinder inner diameter (2rv) 34 to 37 mm

Number of vanes 10

Vane Height (Vh) 7-10 mm

1.8 to 2.5 mm vane thickness

Distance between vane inner ends 2ra 8 to 10 mm

As shown in Fig. 4, the inventors of the present invention provide a magnetron in which the fifth harmonic choke C5 is provided around the second harmonic choke C2 and the antenna 25 at the distal end of the antenna 25. The magnetron tubes of the first to tenth examples and the first to third comparative examples were manufactured in which the dimensions of the first strap ring 14a and the second strap ring 14b were changed as follows in the range of the anode size. In addition, the same code | symbol as FIG. 1 shows the same part. Table 1 shows the results of measuring the characteristics of each harmonic (3f, 5f, 6f, 7f) of these magnetron tubes.

(First strap ring)

External diameter (LS) 17 to 21 ø

Width t 0.5 to 1.5 mm

(Second strap ring)

Internal diameter (SS) 12 to 15 ø

Width t 0.5 to 1.5 mm

In the above examples and comparative examples, the ratio (SS / 2ra) of the distance 2ra between the inner diameter SS of the second strap ring and the vane tip was changed in the range of 1.43 to 1.59.

5 is a graph plotting Table 1, and the relationship between the noise level and the ratio SS / 2ra of the distance 2ra between the inner diameter SS of the second strap ring 14b and the inner end of the vane 13 is shown. Indicates. In addition, although not shown in Table 1, the characteristic of the 2nd harmonic 2f and the 4th harmonic 4f was also shown.

Table 1

SS / 2ra Harmonic 3f 5f 6f 7f First embodiment 1.45 -1.8 (m) -16.0 -50.3 -44.7 Second embodiment 1.45 -5.2 -23.0 -52.5 -45.7 Third embodiment 1.45 -6.5 -17.6 -46.7 -39.6 Fourth embodiment 1.45 -11.8 -20.0 -53.8 -33.3 Fifth Embodiment 1.49 -7.7 -18.8 -53.8 -44.1 Sixth embodiment 1.49 -12.0 -18.3 -50.2 -44.1 Seventh embodiment 1.53 -17.1 -16.3 -55.3 -45.2 Eighth embodiment 1.53 -12.4 -18.4 -58.6 -44.9 9th Example 1.53 -12.9 -17.7 -54.3 -35.4 Tenth embodiment 1.53 -14.7 -24.9 -50.4 -41.6 Comparative Example 1 1.43 -4.1 -19.5 -41.9 -42.3 2nd comparative example 1.58 -19.4 -16.7 -31.4 -32.3 Third Comparative Example 1.59 -16.3 -14.7 -30.4 -36.4

The abscissa in Fig. 5 is SS / 2ra, the ordinate is the noise level ㏈m, and the curves 2f to 7f each represent the noise levels of the second to seventh harmonics in turn.

As shown in Fig. 3, (SS / 2ra) is in the range of 1.45 to 1.53, preferably in the range of 1.48 to 1.52, and the sixth harmonic 6f and the seventh harmonic 7f are suppressed.

The characteristic of the third harmonic 3f is that (SS / 2ra) is in the range of 1.45 to 1.53 and is lowered to the right. Therefore, when suppressing also the 3rd harmonic, it is preferable to set (SS / 2ra) to the value of about 1.53.

Magnetron harmonics are caused by large disturbances in the microwave field in the working space formed at the anode and cathode. Therefore, the suppression of harmonics affects not only a choke having a length of 1/4 of the wavelength? For the purpose of suppressing harmonics on the output side, but also an element such as an anode structure and a pole piece shape, which influence each other. However, FIG. 6 shows suppression characteristics of the sixth harmonic 6f and the seventh harmonic 7f when the fifth harmonic choke C5 is removed from the structure of FIG. The structure without C5 is different from the structure with C5 in Fig. 4, so the operating point is different. However, as seen from the characteristic of Fig. 5, the suppression characteristics of harmonics 6f and 7f are substantially maintained. That is, according to the present invention, the suppression effect of 6f and 7f is secured regardless of the structural change of the output portion, that is, whether or not the fifth harmonic choke is present.

According to the above configuration, it is possible to realize a microwave oven magnetron in which unnecessary noise, in particular, the sixth harmonic and the seventh harmonic is suppressed.

Claims (4)

A cathode located inside the anode cylinder, a plurality of vanes disposed radially from the inner wall of the anode cylinder toward the cathode direction, and a pair of first straps alternately connected to each other above and below the plurality of vanes In a microwave oven magnet having a ring and a pair of second strap rings located inward from the first strap ring and connected alternately one by one above and below the plurality of vanes, each having an oscillation frequency of 2450 MHz band. The inner diameter of the second strap ring is a magnetron for a microwave oven, characterized in that 1.45 times to 1.53 times the distance between the inner end portions of the two vanes positioned on the diameter of the anode cylinder. The magnetron for a microwave oven according to claim 1, wherein an inner diameter of the second strap ring is 1.48 to 1.52 times the distance between the inner ends of the two vanes positioned on the diameter of the anode cylinder. The microwave oven magnet according to claim 1, wherein a ratio (2ra) / (2rv) of the distance (2ra) between the inner ends of the second vanes and the inner diameter (2rv) of the anode cylinder is 0.22 to 0.28. A pole piece and an output portion (an antenna extending from the vane) extend from one end surface of the anode cylinder, and the pole piece and input portion (including a cathode system) from the other end surface of the anode cylinder. And a choke including a choke up to at least a fifth harmonic suppression at the output section, wherein the choke comprises a choke.

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